Electrical measuring instrument.



No. 796,032. PATENTED AUG. 1, 1905.

' T.DUNYCAN.'

ELEOTRIGAL MEASURING INSTRUMENT. v APPLIOATION FILED JUNE 26, 1901.xmwwnn m. 7, 1905.

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wwl QM ATTORNEYS.

UNITED STATES I PATENT OFFICE THOMAS DUNCAN, OF CHICAGO, ILLINOIS,ASSIGNOR TO DUNCAN ELEC- TRIC MANUFACTURING COMPANY, OF LAFAYETTE,INDIANA.

ELECTRICAL MEASURING INSTRUMENT.

Specification of Letters Patent.

Patented Aug. 1, 1905.

Application filed June 26, 1901. Renewed January 7, 1905- Serial No.239,965-

To ctZZ whom, it may concern:

Be it known that I, THOMAS DUNCAN, a citizen of the United States,residing at Chicago,

in the county of Cook and State of Illinois,

factor or difference in phase between the current and impressedelectromotive force. in working circuits. It is desirable to have theelectricians at the generatingstations informed concerning the phase ofthe current with relation to the pressure.

Heretofore it has been the practice to determine power factorsby'dividing the quantity of real watts by the quantity of apparentwatts. For this purpose three instruments were employed-namely, avoltmeter, an ammeter, and a wattmeter. The product of the voltmeter andthe ammeter readings determined the apparent watts, which result wasdivided into thereading of the wattmeter to determine the power factor.This method of determining the power factor involves mental calculationand consumes time where frequently it is desired to know without delaythe actual power, factor of the system. I have devised an instrumentwhich is capable of indicating directly upon asuitable readingscale thepower factor.

Generally speaking,my invention comprises a measuring element and motormeans which is caused to operate upon a change in phase relation of thecurrent and pressure to effect an actuation of the measuring element toindicate the difference of phase between the current and pressure. v Inthe preferred embodiment of my invention I employ two windings which aresubject to the pressure of the system and which produce magnetizingeffects differing in phase, preferably by ninety degrees, and a third, acurrent-winding, which produces a magnetic field varying in phase withthe current in the system and by coaction with the pressurefieldsefiects a'location ofthe measuring element that indicates upon a scalethe phase relation of the current in the main circuit with the pressureimpressed upon that circuit. One of the pressure-fields is preferablymaintained'in phase with the impressed pressure, while the otherpressure-field is maintained in quadrature with the impressed pressure.I do not wish to be limited, however, in all embodiments of my inventionto a quadrature relation between the fields of the pressurewindings norto the phase relations between the pressure-fields and the pressureimpressed upon the working circuit. The pressure fieldwindings may bestationary and the currentwinding may be rotatably mounted. and providedwitha pointer traveling over a suitable scale, or the current-windingmay be maintamed stationary and the pressure-windings may be mounted torotate upon a support, I

upon which pressure windings or support the indicating pointer or needlemay be secured.

I will explain my invention more fully by reference to the accompanyingdrawings, in which- Figure 1 is a diagrammatic view of analternating-current system of distribution, illustrating a power factorindicator connected therewith having stationary pressure field-coils.Fig. 2 is a view of an alternatingcurrent system of transmission havinga power-factor indicator connected therewith provided with movablepressure field-coils. Fig. 3 is a vector diagram illustratinggraphically the manner in which the field due to one of thepressure-windings is brought into phase with the impressed pressure.Fig. 4: is a vector diagram illustrating the manner in which the fielddue to the remaining pressure-winding is brought into quadrature withthe pressure.

Like parts are indicated by similar characters of reference throughoutthe views.

I have illustrated an alternating -current generator 1, that suppliesalternating current to transmission-mains 2 2, that extend from thegenerator to districts of consumption. The power-factor indicator isusually placed at the central station.

Referring more particularly to Fig. 1, the coil3 is connected in bridgeof the mains, a non-inductiveresistanceA being included in the samebridge with the coil 3, by means of which resistance the current throughthe coil is caused to approach closely the pressure in phase. To secureexact coincidence in phase between the magnetism due to thispressurewinding and the impressed pressure, a coil 5 in secondaryrelation to the coil 3 and included in a closed local circuit withreactance, preferably in the form of resistance 6, is employed. As analternative for adjusting the phase of the current in the closed coil 5reactance in the form of inductance 7 may be included in circuittherewith. The adjustment of the phase of the current in coil 3 withrespect to the impressed pressure is illustrated in' the vector diagramFig. 8, wherein (0 represent the impressed pressure; 0 b, the current inand magnetism due to coil 3; 0 a, the secondary electromotive force inthe coil 0 0, the secondary current in and magnetism due to the coil 5,and 0 r the resultant magnetism which is in phase with the impressedelectromotive force 0 a. The other shunt or pressure field-coil 8 hasits current lagging nearly ninety degrees behind the line-pressure. Thiscoil 8 is also connected in bridge of the mains and includes in serieswith it in the same bridge an impedance-coil 9, which causes the currentin said coil 8 to lag as near ninety degrees as possible. To obtain amagnetism that lags exactly ninety degrees with respect to the impressedpressure, I employ a winding 10 in secondary relation to coil 8 andadjust the inductive resistance 11 included in circuit therewith untilquadrature is obtained. This is illustrated bythe vector diagram Fig. 4,in which 0 aindicates the impressed pressure; 0 d, the current in andmagnetism due to coil 8; 0 a, the secondary electromotive force of thecoil 10; 0 f, the secondary current in and magnetism due to coil 10; 0e, the resultant magnetism of the currents 0 cl and 0 fin quadraturewith the impressed pressure.

By means of the coils 8 and 3 and their accessories there is producedmagnetism represented by the magnetic axial line C C due to the coil 3that is in phase with the impressed pressure and a magnetism representedby the magnetic axial line A A due to coil 8 that is in quadrature withthe impressed pressure. The current-winding 12 when movable has currentsupplied to it by means of suitable springs in a well-known way, whichsprings 8 8 constitute the terminals of the winding, to which terminalscurrent. is preferably led from the secondary ofa transformer 13, whichcurrent-winding produces magnetism having a shifting axis B B. Whilethese springs 8 8 might be made very slender, so as to exert practicallyno restraining torque to the motion of the current-coil, (or pressurewindings, if they constitute the movable member, it is found desirablein practice to make these springs of suflicient torsional strength toexert a slight restraining and steadying influence upon the movablememher. On account of this torque exerted by the springs thecurrent-coil under given conditions will not come to rest in' theposition determined by the interacting forces of the cu rrent andpressure windings alone that is to say, if the magnetizations set up bythese windings were such as to of themselves turn the pointer through anangle of thirty degrees from its normal position the pointer will not beturned through so large an angle as thirty degrees on account of therestraining torque exerted by the springs-and the stronger the springsthe greater the difference between the angle determined by themagnetizations and that actually taken by the pointer. Now if for anygiven springs the strength of the magnetizations of the coils or any ofthe coils be increased there will be a greater torsional moment tendingto overcome the restraining torque of the springs, and therefore thepointer will be turned through a greater angle than when themagnetizations are weaker. Having then a scale graduated for any givencurrent strength through the current and pressure coils of theinstrument, it will be apparent that in order to obtain absolutelyaccurate readings it will be necessary to have a constant currentflowing through the windings when a reading is taken, irrespective ofthe pressure or current strength in the system to which the instrumentis applied--that is to say, whenever it is desired to take a reading itwill be necessary by some means always to bring the current flowingthrough the coils to some certain given strength before the reading istaken. To maintain this constancy of current, I employ a graduatedresistance or rheostat 14 in series with the current-winding, more orless of which may be switched into or out of circuit, according to theamount of current in the line. This resistance should be adjusted byplacing the switch opposite the scale-mark upon the scale 15 thatcorresponds to the indication of current in the line upon an ammeter.For example, if the current in the main line is thirty amperes theswitch or pointer of the rheostat 14 is moved to the mark on theamperescale 15. If upon taking another reading the current has reachedforty, the rheostat switch or pointer should be moved to the scale-mark4:0 upon the amperescale, thereby increasing the amount of resistance 14included with the current-winding l2 and maintaining the current in thiswinding at its proper value. The current in the pressure-windings shouldalso be maintained of uniform value, for which purpose a resistance orrheostat 16 is associated with a volt-scale 17, the resistance 16 beingincluded in a conductor that is common to both pressure-circuits, sothat one adjustment of the resistance will effect a duplicate adjustmentof the current flowing through the pressurewindings. As the pressure isincreased the amount of resistance 16 in the pressure-circuits should beincreased. Whenever a readingftherefore, is to be taken, the rheostat 14has its arm placed opposite the scale-mark upon the ampere-scale 15 thatcorresponds to the current in the line, while the rheostat 16 has itsarm adjusted to correspond to the scale-mark upon the volt-scale 17 thatindicates the pressure in the line, so that the coils of the instrumentalways have the same magnetizing effect when readings are taken, the

actuation of the movable member of the instrument then depending solelyupon the phase relations of the magnetism due to the current-windingswith respect to the magnetic fields due to the pressure-windings.

In Fig. 1 the current-winding 12 is movable and has rigidlyattachedthereto an indi eating-needle 18, provided at its free end with Whenthis condition exists, the magnetic fields due to the coils 12 and 3 arein phase and the magnetic axes B B and C C are caused to coincide,whereby the pointer 18 is rotated to the right until it registers withscale-mark 1, indicating that the angle of lag is zero and that therejsone-hundred-per-cent. power factor. If the current should lag ninetydegrees behind the pressure, the magnetic fields due to the coils 8 and12 would be in phase and the magnetic axes A A and B B wouldcoincide,whereby the needle isshifted toward the left until it registered withthe scale-mark 0, indicating the greatest angle of lag and a powerfactor of zero. If there is a phase difference between the current andpressure of eighty-four degrees plus, the indicator 18 will register atapproximately .1,'indicating a power factor of ten per cent. If thereshould be a phase diflerence of seventy-eight degrees plus, the needle18 will register at .2, indicating a power factor of twenty per cent.Phase angles seventy-two degrees plus,

sixty-six degree plus, sixty degrees plus, fiftythree degrees plus,forty-five degrees plus, thirty-six degrees plus, and twenty-fivedegrees plus correspond approximately with power factors .3," .4, .5,.6',.7, .8, and .9. A readingof the power-factor scale therefore notonly indicates the actual power factor, but may serve to indicate thephase angle between the current and pressure in the working circuit.

I have shown one means for preserving the required ratio between themagnetizing effects of the windings of themotor member to produce auniform effective torque to secure the same movement of the indicatorfor currents of different volume and pressure in which the current andpressure have the same reln my invention, it is obvious that changes'maybe readily made without departing from the spirit thereof, and I do not,therefore,wish to be limited to the precise construction hereindisclosed; but,

Having thus described my invention, I claim as new, and desire tosecure'by Letters Patent, the following:

'1 The combination with an alternatingcurrent system of distribution, oftwo pressure-windings producing fields in quadrature with each other andsupplied with current from the said system, a current-winding suppliedwith current from the said system,a measuring element subjected to thetorque of the said current and pressure windings to indicate the phasedifference between the current and pressure in the system ,and means formaintaining the current in the pressure and current windingsuniform,irrespective of the voltage and current in the working circuit,substantially as described.

2. The combination with an alternatingcurrent system of distribution, oftwo pressure-windings producing fields in quadrature with each' otherand supplied with current from the said system, a current-windingsupplied with current from the said system, the current-winding beingmovable with relation to the pressure-windings, while thepressurewindings are fixed with relation to each other,

a measuring element mounted upon the movable member of the instrumentand serving to indicate the phase difference between the current andpressure in the system, and means for maintaining the current in thepressure and current windings uniform, irrespective of the voltage andcurrent in the working circuit, substantially as described.

8. In an instrument of the class described, the combination withpressure windings adapted to produce fields in quadrature, acurrent-winding, means whereby the magnetism due to the current-windingis in phase with that due to one of the pressure-Windings when thecurrent and pressure in the working circuit are in phase, and wherebythe magnetism due to the current-winding is in phase with the remainingpressure-winding when the current and pressure are ninety degrees out ofphase, a movable measuring element subject to the torque between thewindings of the meter, serving to indicate the phase difference betweenthe current and pressure, and means whereby the magnetic fields due tothe currents in the current and pressure windings may be maintainedconstant irrespective of the voltage and current in the working circuit,substantially as described.

4. In an instrument of the class described, the combination withrelatively fixed pressurewindings adapted to produce fields inquadrature, a current-winding relatively movable with respect to thepressure-windings, means whereby the magnetism due to the currentwindingis in phase with that due to one of the pressure-windings when thecurrent and pressure in the working circuit are in phase, and wherebythe magnetism due to the currentwinding is in phase with thatdue to theremaining pressure-winding when the current and pressure are ninetydegrees out of phase, a measuring element movable with the current orpressure windings to indicate the phase difference between the currentand pressure in the working circuit, and means whereby the magneticfields due to the currents in the curv rent and pressure windings maybemaintained described.

5. The combination with an alternating-current system of" distribution,of a measuring element, means operated by the current in the system forelfecting movement thereof to indicate the difference in phase betweenthe current and pressure, and means whereby the indications of saidmeasuring element may be independent of variations of current andpressure of the system, substantially as described.

6. The combination with an alternating-current system of distribution,of current and pressure field-windings energized by the current in thesystem, a movable measuring element, the said windings exerting torqueupon the movable measuring element to indicate the phase diflerencebetween the current and the pressure in the system,-and means wherebythe indications of said measuring element may be independent ofvariations of current and pressure of the system, substantially asdescribed.

7. The combination with an alternating-current system of distribution,of two pressurewindings producing fields in quadrature with each otherand supplied with current from the said system, a current-windingsupplied with currentfrom the said system, a measuring element subjectedto the torque of the said current and pressure windings to indicate thephase difference between the current and pressure in the system, andmeans whereby the indicat1ons of said measuring element may beindependent of variations of current and pressure of the system,substantially as described.

8. The combination with an alternating-current system of distribution,of current and pressure field-windings energized by the current in thesystem, creating fields out of phase, a movable measuring element toindicate the phase difference between the current and the pressure inthe system, and means whereby the indications of said measuring elementmay be independent of variations of current and pressure of the system,substantially as described.

9. The combination with an alternating-current system of distribution,of two pressurewindings producing lields out of phase and supplied withcurrent from the said system, a current-winding supplied with currentfrom the said system, a measuring element subjected to the torque of thesaid current and pressure windings to indicate the phase differencebet-ween the current and pressure in the system, and means whereby theindications of said measuring element may be independent of variationsof current and pressure of the system, substantially as described.

10. The combination with an alternatingcurrent system of distribution,of current and pressure field-windings energized by the'current in thesystem, a movable measuring element, the said windings exerting torqueupon the movable measuring element to indicate the phase difierencebetween the current and the pressure in the system, and means wherebythe indications of said measuring element may be independent ofvariation of current and pressure of the system, the current-windingbeing movable with relation to the pressure-windings, the indicatingelement of the meter traveling with the movable winding, substantiallyas described.

11. The combination with an alternatingcurrent system of distribution,of two pressure-windings producing fields in quadrature with each otherand supplied with current from the said system, acurrent-windingsupplied with current from the said system, a

'measuring element subjected to the torque of the said current andpressure windings to indicate the phase difference between the currentand pressure in the system, and means whereby the indications of saidmeasuring element may be independent of variations in the current andpressure of the system, the current-winding being movable with relationto the pressure-windings, the indicating element of the meter travelingwith the movable winding, substantially as described.

12. The combination with an alternatingcurrent system of distribution,of eurrentand pressure field-windings energized by the'current in thesystem, creating fields out of to the pressure-windings, the indicatingelement of the metertraveling with the movable winding, substantially asdescribed.

. 13. The combination with an alternatingcurrent system of distribution,of two pressure-windings producing fields out of phase and supplied withcurrent from the said system, a current-winding supplied with currentfrom the said system, a measuring element subjected to the torque of thesaid current and pressure windings to indicate the phase differencebetween the current and pressure in the system, and means whereby theindications of said measuring element may be independent of variationsin the current and pressure of the system, the current-winding beingmovable with relation to the pressure-windings, the indicating elementof themeter traveling with the movable winding, substantially asdescribed.

14:. In an instrument of the class described, the combination withpressure field-windings producing fields difiering in phase, of acurrent field-winding, an indicating element actuated by the windings ofthe instrument, and rheostats in circuit with the current and pressurewindings for adjusting the currents in these windings with respect tothe current and pressure in the system associated with the meter,substantially as described.

15. In an instrument of the class described, the combination withpressure-windings producing fields differing in phase, of a currentfield-Winding, an indicating element actuated by the windings of theinstrument, and means for adjusting the current in these windings tocompensate for variation in pressure and current of thework-circuit,substantially as described.

16. The combination with an alternatingcurrent system of distribution,of a currentwinding and a pressure-winding receiving current from thesaid system, an indicating device actuated upon variation in phasebetween the fields produced by the said windings to indicate the phasedisplacement between the current and pressure in the system, and meanswhereby the required magnetizing eifects in the current and pressurewindings are secured to eliminate the effects due to variation in theconditions of the circuit, substantially as described.

17. The combination with an alternating current system of distribution,of a currentwinding and a pressurewinding receiving current from thesaid system and produclng fields coinciding in phase when the currentand pressure in the system are coincident in phase, an indicating deviceactuated upon va- .riation in phase between the fields produced by thesaid windings to indicate the phase displacement between the current andpressure in the system, and means whereby the required magnetizingeffects in the current and pressure windings are secured to eliminatethe effects due to variation in the load conditions of the circuit,substantially as described.

18. The combination, in an alternating-current system of distribution,of a measuring element, means operated by the current in the system foreffecting movement thereof to indicate the difference in phase betweenthe current and pressure, and adjustable resistances included in circuitwith said measuring element and said means, substantially as described.

19. The combination, with an alternatingcurrent system of distribution,of current and pressure field-windings energized by the current in thesystem, a movable measuring element, thesaid windings exerting torqueupon the movable measuring element to indicate the phase differencebetween the currentand pressure in the system, and an adjustableresistance included in series with said fieldwindings, substantially asdescribed.

20. The combination with an alternating- -current system ofdistribution, of two pressure-windings producing fields in quadraturewith each other and supplied with current from the said system, acurrent-winding supplied with current from the said system, a measuringelement subjected to the torque of the said current and pressurewindings to indicate the difference between the current and pressure inthe system, and adjustable rheostats included in series with saidWindings, substantially as described.

21. The combination with an alternatingcurrent system of distribution,of two pressure-windings producing fields in quadrature with each otherand supplied with current from the said system, a current-windingsupplied with current fromthe said system, the current-winding beingmovable with relation to the pressure-windings while thepressurewindings are fixed with relation to each other, a measuringelement mounted upon the movable element of the instrument and servingto indicate the phase difiierence between the current and pressurein thesystem, and adjustable rheostatsassociated with said current andpressure windings, substantially as described.

22. The combination with an alternatingcurrent system of distribution,of current and pressure field-windings energized by the current in thesystem, a movable measuring instrument, the said windings exertingtorque upon the movable measuring .element to indicate the phasedifference between the current and pressure in the system, and means formaintaining the current in the current and pressure windings uniform,irrespective of the voltage and current in the working circuit,substantially as described.

23. The combination with an alternatingcurrent system of distribution,of two pressure-windings producing fields out of phase and supplied withcurrent from the said system, a current-Winding supplied with currentfrom the said system, a measuring element subjected to the torque of thesaid current and pressure windings to indicate the phase differencebetween the current and pressure in the system, and means formaintaining the current in the pressure and current windings uniformirrespective of the voltage and current in the working circuit,substantially as described.

24. The combination with an alternating current system of distribution,of two pressure-windings producing fields in quadrature with each otherand supplied with current from the said system, a current-windingsupplied With current from the said system, a measuring elementsubjected to the torque of the said current and pressure windings toindicate the phase difference between the current and pressure in thesystem, and means for maintaining the ratio between the currents in thecurrent and pressure field-windings irrespective of the voltage in thesystem, substantiall y as described.

25. The combination with an alternatingcurrent system of distribution,of current and pressure field windings energized by the agency of thecurrent in the system, a mov' able measuring element, the said windingsexerting torque upon the movable measuring element to indicate the phasediflierence between the current and the pressure in the system, andmeans for maintaining the ratio between the current and the pressurewindings irrespective of changes in the system, substantially asdescribed.

26. The combination with an alternatingcurrent system of distribution,of current and pressure field windings energized by the agency of thecurrent in the system, a movable measuring element, the said windingsexerting torque upon the movable measuring element to indicate the phasediflereuce between the current and the pressure in the system, and meansfor preventing modification in the operation of the instrument bychanges in load conditions, substantially as described.

In witness whereof I hereunto subscribe my name this 23d day of May, A.D. 1901.

THOMAS DUNCAN.

Witnesses:

GEoReE L. CRAGG, HERBERT F. OBERGEELL.

